You will only get a friction shifter off an old bike these days, just ring up and ask them to count how many gears there are on the back and get a cheap shifter to suit. sjscycles.co.uk are a good place to look as they stock owt from 6 speed upwards. (a 6 speed will work with a five speed freewheel if you can't find a 5 speed shifter, you may just have to drop down two then back up one to change down into 4th and fifth, but if so the indexing will work ok once in gear.)
Surely just ask your Mum (or someone down there!) to count the number of cassette rings (even a non-cyclist can do that) and buy the appropriate shifter. If it's less than 7, SJS, as noted above, have loads of old Suntour & cheapo Shimano thumbies that'd do the job.
but it needs a new shifter for the rear mech
